Device and method for solar power generation

ABSTRACT

A photovoltaic device comprising an array of elongate reflector elements mounted substantially parallel to one another and transversely spaced in series, at least one of the reflector elements having an elongate concave reflective surface to reflect incident solar radiation towards a forward adjacent reflector element in the array. The at least one reflector element includes a photovoltaic receptor mounted on the reflector element by a mounting arrangement to receive reflected solar radiation from a rearward adjacent reflector element. The reflector element also includes a heat sink in heat transfer relationship with the photovoltaic receptor, thermally isolating the photovoltaic receptor, at least partially, from the reflector element.

TECHNICAL FIELD

The present application relates generally to the technical field ofsolar power generation, in one specific example, to a photovoltaicdevice. The application extends to a mounting unit and to a method ofconverting solar radiation to electrical power.

BACKGROUND

Various devices and systems are known for use in harvesting solar energyby the use of photovoltaic cells. These include slat concentrators,which are photovoltaic devices generally comprising a series of paralleltrough-shaped off axis parabolic reflectors to concentrate sunlight onphotovoltaic receptors mounted on respective adjacent reflectors. Thereflectors are typically automatically actuated to track the sun inorder to ensure accurate reflection and concentration of solar radiationon the photovoltaic receptors.

The photovoltaic receptors forming part of such concentrators have alimited lifespan and the photovoltaic devices therefore require periodicremoval and replacement of the photovoltaic receptors. There is arelationship between the operating temperatures of the photovoltaicreceptors and their lifespan. Additionally, a photovoltaic receptorgenerally displays higher efficiency at lower temperatures.

SUMMARY

In accordance with a first embodiment there is provided a photovoltaicdevice comprising an array of elongate reflector elements mountedsubstantially parallel to one another and transversely spaced in series,at least one of the reflector elements having an elongate concavereflective surface to reflect incident solar radiation towards a forwardadjacent reflector element in the array. The at least one reflectorelement includes a photovoltaic receptor mounted on the reflectorelement by a mounting arrangement to receive reflected solar radiationfrom a rearward adjacent reflector element. The reflector element alsoincludes a heat sink in heat transfer relationship with the photovoltaicreceptor, thermally isolating the photovoltaic receptor, at leastpartially, from the reflector element.

The heat sink may include a set of cooling fins located between thephotovoltaic receptor and the associated reflector element. A mountingarrangement may include a thermal expansion arrangement to compensatefor varying rates of thermal expansion and contraction of thephotovoltaic receptor and the mounting arrangement.

In accordance with a further embodiment, the reflector element includesa secondary optic device directing solar radiation reflected on to it bya rearward adjacent reflector element on to the associated photovoltaicreceptor. The secondary optic device may include a secondary reflectormounted on the reflector element adjacent the photovoltaic receptor.

A. BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments are illustrated by way of example and not limitation inthe figures of the accompanying drawings, in which like referencenumerals indicate like parts, unless otherwise indicated. In thedrawings:

FIG. 1 is a three-dimensional view of a photovoltaic device inaccordance with an example embodiment.

FIG. 2 is a sectional side view of the photovoltaic device in accordancewith the example embodiment of FIG. 1, taken along line II-II in FIG. 1.

FIG. 3 is a three-dimensional view, on an enlarged scale, of part of areflector element forming part of a photovoltaic device in accordancewith the example embodiment of FIG. 1.

FIG. 4 is partial, exploded three-dimensional view of a photovoltaicassembly forming part of a photovoltaic device in accordance with theexample embodiment of FIG. 1.

FIG. 5 is a longitudinal sectional view of a photovoltaic assembly inaccordance with the example embodiment of FIG. 4, taken along line V-Vin FIG. 4.

FIG. 6 is a side view of part of a photovoltaic device in accordancewith another example embodiment.

FIG. 7 is an isolated side view, on an enlarged scale, of a second ofthe optic device forming part of a photovoltaic device in accordancewith the example embodiment of FIG. 6.

FIG. 8 is an isolated side view of a secondary optic device inaccordance with another example embodiment.

FIG. 9 is an isolated side view of a secondary optic device inaccordance with a further embodiment.

FIG. 10 is a partial three-dimensional view of a photovoltaic assemblyforming part of a photovoltaic device in accordance with yet a furtherexample embodiment.

FIG. 11 is a cross-sectional end view of the photovoltaic assembly inaccordance with the example embodiment of FIG. 10, taken along line X-Xin FIG. 10.

FIG. 12 is a partial three-dimensional view of a photovoltaic assemblyforming part of a photovoltaic device in accordance with yet anotherexample embodiment.

DETAILED DESCRIPTION

Example photovoltaic devices and solar power generation methods aredescribed. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of example embodiments. It will be evident, however, toone skilled in the art that the embodiments may be practiced withoutthese specific details.

In the drawings, reference numeral 10 generally indicates a photovoltaicdevice in accordance with an example embodiment. As can be seen in FIG.1 of the drawings, the device 10 is a slat concentrator comprising anarray of reflector troughs or reflector elements 17 which are mounted ona rigid frame 11. The frame 11 is displaceably connected by struts 22 toan anchored support in the form of a pair of pylons 14. In particular,the frame 11 may be pivotally displaceable about an operativelyhorizontal axis 13 to permit tracking of the sun, in order to assistwith optimal orientation of the reflector elements 17 relative to thesun. The device 10 further includes a control arrangement to controlpivotal displacement of the frame 11 about the axis 13.

The reflector elements 17 are substantially parallel to one another,being transversely spaced in series at regular intervals, so thatlongitudinal axes of the respective reflector elements 17 lie in acommon plane. A reflector element 17 includes a mirror or reflectivesurface 16 to reflect and concentrate incident solar radiation orsunlight 54 on to a photovoltaic receptor 30 (see FIGS. 3-5) formingpart of a photovoltaic assembly 20 mounted on a forward adjacentreflector element 17.

In an example embodiment, one or more reflector elements 17 includes anelongate plate member 18 of sheet material or plate material, the platemember 18 being held in place by a mirror support 24 (see FIG. 3) and abottom support 32 connected respectively to a top edge and a bottom edgeof the plate member 18. The mirror support 24 and the bottom support 32extend between side rails 12 forming part of the frame 11, being fastwith side rails 12. An upwardly directed surface of the plate member 18has a reflective covering or coating, thus providing the reflectivesurface 16. In other embodiments, the reflective surface 16 may beprovided by a mirror. The plate member 18 is curved, so that thereflective surface 16 is concave and has a constant cross-sectionalprofile along its length. In an option, each plate member 18 is curved.The reflector element 17 may provide an off-axis cylindrical parabolicmirror.

As can be seen in FIG. 2, the reflector elements 17 are positioned suchthe respective reflective surfaces 16 reflect and concentrate incidentsunlight 54 on the photovoltaic assembly 20 mounted on the top edge ofthe forward adjacent plate member 18. For ease of illustration, the pathtravelled by incident sunlight 54 reflected by the reflective surfaces16 is shown for only one of the reflector elements 17. Because thereflective surface 16 is elongate and has a constant sectional profile,the reflective surface 16 reflects and concentrates sunlight 54 on to alongitudinally extending target band on a rear of its forward adjacentreflector element 17. In an example embodiment, the reflective surfaces16 have a concentration ratio of about 10, by which is meant that thearea of the target band is 1/10 the area of incident sunlight on thereflective surface 16.

The photovoltaic assembly 20 includes a photovoltaic receptor in theform of an elongate photovoltaic laminate or strip 30 of photovoltaiccells (see FIGS. 2-4). The photovoltaic strip 30 is mounted on therespective reflector element 17 by a mounting arrangement, which holdsthe photovoltaic strip 30 in position such that an active face 50 (FIG.4) of the photovoltaic strip 30 is located in the target band ofsunlight 54 reflected by the reflective surface 16 of a rearwardadjacent reflector element 17. The photovoltaic strip 30 converts solarenergy into electrical power.

The mounting arrangement includes a heat sink 26 which is in heattransfer relationship with the photovoltaic strip 30, thermallyisolating the photovoltaic receptor 30 from the reflector element 17 onwhich it is mounted. By “heat sink” is meant an object or system thatabsorbs and dissipates heat in order to protect heat-sensitivecomponents. The mounting arrangement includes a heat sink base in theform of a photovoltaic receptor holder 27 provided by a series of holdersections 28 which are longitudinally aligned end-to-end. As can best beseen in FIGS. 3 and 4, the holder section 28 comprises a flat backingplate 36, a pair of shallow webs 37 which project perpendicularly awayfrom opposite side edges of the backing plate 36, and a pair of lips 38which are parallel to the backing plate 36 and project towards eachother from lower edges of the webs 37, to define between them alongitudinally extending slit 39 exposing the active face 50 of thestrip 30.

The holder section 28 thus defines a shallow rectangular holding cavitywhich is complementary in cross-sectional profile to the cross-sectionaloutline of the photovoltaic strip 30. The holder sections 28 have openends, so that the respective holding cavities of the sections 28together define an elongate slot 43 in which the photovoltaic strip 30is matingly received. The active face 50 of the photovoltaic strip 30 isin register with the slit 39 for receiving reflected and concentratedsunlight 54, while a reverse face 51 of the photovoltaic strip 30 bearsagainst the backing plate 36. The reverse face 51 of the photovoltaicstrip 30 may be bonded to the backing plate 36 by a thermally conductiveadhesive, to permit conductive heat transfer between the strip 30 andthe backing plate 36. Because the holder sections 28 have constantcross-sectional profiles and open ends, the photovoltaic strip 30 may beslidingly receivable, socket/spigot fashion, in the composite holder 27formed by the sections 28.

The lips 38 bear against the active face 50 of the photovoltaic strip30, anchoring the strip 30 against movement transversely away from thebacking plate 36. Portions of the active face 50 adjacent its side edgesare obscured by the lips 38, and that solar cells on the active face 50of the photovoltaic strip 30 may be concentrated in a centrallongitudinally extending band which is in register with the slit 39. Ascan be seen in FIGS. 2 and 3, the photovoltaic strip 30 is mounted bythe holder 27 on the associated plate member 18 to face rearwards anddownwards at an angle towards the rearward adjacent reflector element17. The strip 30 is mounted on the associated reflector element 17 suchthat the target band of the rearward adjacent reflective surface 16coincides with the slit 39 of the holder 27.

Adjacent ends of neighboring holder sections 28 are spaced by a thermalexpansion gap 42. The series of expansion gaps 42 form a thermalexpansion arrangement to compensate for thermal expansion of thephotovoltaic strip 30 and the composite holder 27 at differing rates. Inan example embodiment, the holder 27 is of a metal with a relativelyhigh thermal conductivity coefficient, for instance being of aluminum[PLEASE CONFIRM], while the strip 30 is a laminate, which may include alayer of glass. In other embodiments, the holder 27 may, instead ofbeing comprised of separate sections 28, be of monolithic or unitaryconstruction while still including a thermal expansion arrangement suchas, for example, regularly spaced openings or cuts.

In an embodiment, the heat sink 26 is in the form of a set of metalcooling fins 40. The fins 40 are parallel to one another and aretransversely spaced in a series which extends along at least a portionof the length of the associated reflector element 17 (FIGS. 3 and 5).The fins 40 therefore lie in respective operatively upright planes. Thefins 40 may be disposed perpendicularly to the longitudinal axis of theplate member 18, so that, when the plate member 18 is disposedhorizontally, the fins 40 are oriented vertically, to permit the passageof rising air through gaps between the fins 40. The set of cooling fins40 is constructed such that, in longitudinal section, the fins 40describe successive U-shaped profiles, so that the fins 40 projectcantilever-fashion from a base 41. The base 41 of the set of fins 40 isconnected face-to-face to a stiffening plate 46 which, in turn, ismounted on the associated plate member 18, as described in more detailbelow. The fins 40 are therefore anchored at their proximal ends, theholder sections 28 being connected to free or distal ends of the fins40. In other words, the holder section 28 is connected to a bed of a finend edges which respectively extend transversely across the width of theholder section 28. As can be seen in FIG. 4, the sections 28 and thefins 41 are more or less equal in width. With reference to FIG. 5, itwill be noted that the thermal expansion gaps 42 are positioned betweenadjacent fins 40. Provision of the expansion gaps 42 permits somemovement of holder sections 28 in their longitudinal direction relativeto the stiffening plate 46, by elastic cantilevered flexing of the fins40 connected to the holder sections 28. The structural unit formed bythe stiffening plate 46, the set of cooling fins 40 and the holder 27 istherefore uninterrupted on one side, i.e. at the stiffening plate 46,while having regularly spaced breaks or interruptions provided by thethermal expansion gaps 42 on an opposite side.

The cooling fins 40 form part of the mounting arrangement, spacing theholder 27 and the photovoltaic strip 30 from the associated plate member18 to form a convection gap 44 between the stiffening plate 46 and theheat sink base 28. This allows cooling of the fins 40, and hence coolingof the heat sink base 28 and the photovoltaic strip 30, by the passageof air due to natural convection through the convection gap 44.

In other embodiments, a set of cooling fins forming the heat sink mayhave a different construction. For example, the fins may be formedthrough moulding, casting or extrusion. The set of fins may instead befolded fins, for instance a continuous folded metal strip, or the finsmay be stacked or skived fins. In yet other embodiments, the heat sinkmay be provided by pin fins.

The photovoltaic strip 30, the holder 27, the heat sink 26 and thestiffening plate 46 together form the photovoltaic assembly 20 whichfunctions as a modular element, being removably and/or replaceablymounted on the associated plate member 18. In an example embodiment, themodular assembly 20 is mounted on the plate member 18 by the mirrorsupport 24 (FIG. 3). The mirror support 24 is, in an option, in the formof an extrusion which extends along the length of the plate member 18and defines a recess 58 clipped on to an upper edge of the plate member18, to connect the mirror support 24 to the plate member 18 at its upperedge. The mirror support 24 also has a snapfit formation in the form ofa pair of longitudinally extending lips or snap lugs 48 which are insnapfit engagement with the modular assembly 20, to hold the modularassembly 20 in position. As can be seen in FIG. 4, the modular assembly20 includes a complementary snapfit formation comprising snap recessesor notches 52 in both side edges of the cooling fins 40 adjacent theirproximal ends, to receive the complementarily shaped snap lugs 48. Thenotches 52 thus provide a connection arrangement for removably andreplaceably connecting the assembly 20 to the mirror support 24. Themirror support 24 performs the dual functions of, on the one hand,supporting an upper edge of the plate member 18, and, on the other hand,connecting the assembly 20 to the plate member 18.

In use, the frame 11 is controlled by a control arrangement to track thesun by pivotal displacement of the frame 11 about the pivot axis 13.Incident sunlight 54 is reflected and concentrated by the reflectivesurface 16 on to the photovoltaic assembly 20 mounted on the neighboringreflector element 17 in front of it. The concave parabolic reflectivesurface 16 concentrates sunlight 54 falling on it on to a target bandcoinciding with the slit 39 in the holder 27 of the forward adjacentreflector element 17. The sunlight 54 is therefore reflected andconcentrated on the active face 50 of the adjacent photovoltaic strip 30exposed by the slit 39, resulting in the generation of electric power bythe photovoltaic strip 30.

Due to its exposure to and absorption of concentrated sunlight 54, thephotovoltaic strip 30 increases in temperature. Excessive heating of thephotovoltaic strip 30 may adversely affect its conversion efficacy andlife expectancy. However, the photovoltaic strip 30 is cooled, in use,by heat exchange with the heat sink 26. Heat is transferred from thephotovoltaic strip 30 by conduction to the backing plates 36 with whichthe strip 30 is in thermally conductive contact. It will be appreciatedthat the photovoltaic strip 30 will tend to separate from the backingplate 36 under gravity, owing to the orientation of the assembly 20, andthat the provision of a thermally conductive bonding between the reverseface 51 of the strip 30 and the backing plates 36 promotes thermalconduction between the strip 30 and the backing plates 36.

The backing plates 36 are in turn connected to the cooling fins 40 in aconductive heat transfer relationship, so that heat received by thebacking plates 36 is transferred to the cooling fins 40. The coolingfins 40 are cooled by ambient air passing through gaps between thecooling fins 40 due to natural convection. Excessive heat in thephotovoltaic strip 30 is thus dissipated by the heat sink 26. Suchpassive cooling due to convection is promoted by the upright orientationof the cooling fins 40 and positioning of the modular assemblies 20 neartop edges of the plate members 18. Rising air is thus guided by anunderside of each plate member 18 towards and through the cooling fins40, while upright orientation of the cooling fins 40 results in minimalbaffling or obstruction of air passing through the heat sink 26.

In use, the photovoltaic strip 30 and the holder 27 experiencetemperature variations and consequently change in length due to thermalexpansion and contraction. However, the strip 30 and holder 27 expandand contract at different rates, owing to differences in their materialproperties. The expansion gaps 42 compensate for thermal expansion andcontraction of the strip 30 and the holder 27 at different rates, toameliorate internal stresses in the photovoltaic strip 30. It is to benoted that connection of the holder sections 28 to the distal ends ofthe fins 40 allows substantially unrestrained lengthening and shorteningof the holder sections 28, as well as longitudinal movement of theholder sections 28 relative to one another, due to cantilevered elasticflexing of the fins 40.

Removable and replaceable mounting of the modular assemblies 20 on theplate members 18 facilitates removal and replacement of the photovoltaicstrip 30. When a strip 30 reaches the end of its lifetime, the modularassembly 20 is removed as a unit and is replaced by a photovoltaicassembly 20 with a new photovoltaic strip 30. Such removal andreplacement of the photovoltaic assemblies 20 is achieved by snapfitengagement of the snap lugs 48 with the notches 52.

Furthermore, the holder 27, the cooling fins 40 and the stiffening plate46 forms a mounting unit which is reusable by removal and replacement ofthe photovoltaic strip 30. Such removal and replacement is achieved bysliding movement of the strip 30 in the slot 39 provided for it by thealigned holder sections 28.

The example embodiment extends to a solar power installation (not shown)or solar power plant comprising a multitude of the photovoltaic devices10 installed in a common location and electrically connected togetherfor the generation of electrical power. It is to be noted that readyremoval and replacement of the photovoltaic assemblies 20 isparticularly advantageous in such a solar power installation, as itreduces on-site maintenance loads.

FIG. 6 shows part of another example embodiment of a photovoltaic device70. Similar to the device 10 of FIG. 1, the device 70 of FIG. 6comprises an array of parallel reflector elements 80 with respectiveoff-axis parabolic reflective surfaces 16 to reflect sunlight 54 on to aphotovoltaic strips 30 mounted on adjacent reflector element 80. Forease of illustration, only two of the reflector elements 80 are shown inFIG. 6. In the example embodiment of FIG. 6, each reflector element 80is an extruded hollow metal element having a front side which forms thereflective surface 16, and a rear side on which the photovoltaic strip30 is mounted.

As can best be seen in FIG. 7, each reflector element 80 includes asecondary optic device 82 to direct sunlight 54 which falls on thesecondary optic device 82 on to the photovoltaic strip 30. In theexample embodiment, the secondary optic device 82 includes a recess inthe form of a trough or channel 112. The channel 112 is generallysplayed U-shaped in cross-sectional outline, having a base with opposedside walls 84 diverging from opposite side edges of the base. Each ofthe side walls 84 of the channel 112 has a reflective covering orcoating, thus forming a secondary reflector for reflecting sunlight onto the photovoltaic strip 30. The photovoltaic strip 30 is located onthe base of channel 112, with the active face 50 of the photovoltaicstrip 30 facing towards an open mouth of the channel 12.

The device 70 further includes a heat sink 86 comprising a verticallyspaced series of horizontally extending cooling fins which areintegrally formed with the extruded element 80. In other embodiments,the cooling fins of the heat sink 86 may have an upright orientation. Inanother embodiment, the positions of the heat sink 86 and the secondaryoptic device 82 may be inverted, so that heat sink 86 is positionedadjacent a top edge of the reflector element 80, the secondary opticdevice being located below the heat sink 86.

In operation, sunlight 54 is reflected and concentrated by thereflective parabolic surface 16 of each reflector element 80 towards thechannel 112 and photovoltaic strip 30 of a forward adjacent reflectorelement 80. As can be seen in FIG. 7, the orientation of the reflectiveside walls 84 of the channel 112 relative to the parabolic reflectivesurface 16 of the rearward adjacent reflector element 80 is such thatany sunlight 54 reflected by the parabolic reflective surface 16 intothe channel 112 is further reflected by the reflective side walls 84 ofthe channel 112 on to the photovoltaic strip 30. The reflective sidewalls 84 of the channel 112 direct on to the photovoltaic strip 30sunlight 54 reflected on to them by the rearward adjacent parabolicreflective surface 16.

Provision of the secondary optic device 82 effectively widens the targetband on which sunlight has to be reflected by the parabolic reflectivesurface 16 in order for the sunlight 54 to impinge on the photovoltaicstrip 30. Because of this wider target band or target area, the marginfor error in tracking the sun photovoltaic strip 30 is reduced,advantageously allowing for use of less accurate, and therefore lessexpensive control arrangements. In an example, the device 70 has atracking margin for error of 2-3°, as opposed to a tracking error of 1°without the secondary optic device 82. The device 70 is also more robustdue to the secondary optic device 82, as the device 70 is less sensitiveto misdirection of reflected light owing to warping or relativedisplacement of component parts of the device 70.

Furthermore, the concentration factor or ratio may be increased, so thatmore sunlight is directed on to the photovoltaic strip 30 than would bethe case without the secondary optic device 82. In an example, theconcentration ratio of the device 80 may be improved from 10 to 20 bythe secondary optic device 82. Such greater concentration of sunlight onto the photovoltaic strip 30 results in a reduction in the amount, i.e.the total area, of photovoltaic strip or solar cells needed to generatea given amount of electrical energy, thus increasing the costeffectiveness of the device 80. It will be appreciated that in exampleembodiments where the secondary optic device 82 doubles theconcentration ratio, the photovoltaic cell area may be halved.

FIG. 8 shows another embodiment of a secondary optic device 90, whichincludes a bifacial photovoltaic strip 92 and forms part of an extrudedreflector element 91. The strip 92 has two oppositely outwardly facingmajor surfaces 94 which contain solar cells for the conversion ofsunlight to electric power. In an option, both major surfaces 94 containsolar cells. Similar to the secondary optic device 82 of FIG. 6, thesecondary optic device 90 of FIG. 8 includes a longitudinally extendingchannel 95 with reflective interior walls 84. In an example, the channel95 is U-shaped in cross-sectional outline, with orthogonal orperpendicular side walls and a flat base wall.

The bifacial photovoltaic strip 94 is longitudinally aligned with thechannel 95 and is mounted centrally in a mouth of the channel 95. Thestrip 94 is therefore flanked by longitudinally extending openings 97leading into the interior of the channel 95.

In operation, sunlight reflected and concentrated by an adjacentreflector element 91 may strike an outwardly directed face 94 of thestrip 92, or may be reflected by the reflective interior walls 84 of thechannel 95 on to the inwardly directed face 94 of the strip 92. This isillustrated with reference to two representative reflected rays numbered96 and 98 in FIG. 8. Ray 96, for example, falls directly on theoutwardly directed face 94 of the strip 92, while ray 98 passes throughone of the openings 97 flanking the strip 92, and is reflected first bya side wall 84 and then by the base, so that it impinges on the inwardlydirected face 94 of the strip 92. It is to be noted that the particularcross-sectional shape of the channel 95, as well as the positioning ofthe strip 92, can be varied in other embodiments. For instance, thechannel 95 can, in other embodiments, have a true paraboliccross-sectional outline so that the channel 95 forms a parabolicreflector, with the strip 92 being mounted at a focal point of theparabolic reflector.

In other embodiments, a secondary optic device mounted on a reflectorelement may comprise one or more lenses to concentrate and/or directreflected sunlight on to a photovoltaic receptor.

FIG. 9 illustrates yet a further embodiment of a secondary optic device100 forming part of a reflector element 101. The secondary optic device100 of FIG. 9 is similar in configuration to the secondary optic device82 of FIGS. 6 and 7. In the embodiment of FIG. 9, a channel 102 of thesecondary optic device 100 has a segmented, curved U-shapedcross-sectional outline, roughly approximating a parabolic curve. Asillustrated in FIG. 9, the channel 102 has reflective interior walls 104to reflect sunlight received from an adjacent reflector element 101 ontothe photovoltaic strip 30 located at a base of the channel 95.

FIGS. 10 and 11 illustrate another embodiment of a modular photovoltaicassembly 110 for mounting on a reflector element in a photovoltaicdevice similar to the device 10 illustrated in FIGS. 1-5. The modularassembly 110 of FIGS. 10 and 11 combines the provision of a heat sink116 between a photovoltaic strip 30 and an associated reflector element(not shown in FIGS. 10-12) with the provision of a secondary opticdevice similar to the embodiments described with reference to FIGS. 6-9.

The modular assembly 110 thus includes a splayed U-shaped recess 112with reflective longitudinally extending side walls 84, a photovoltaicstrip 30 being mounted at a base of the recess 112 such that its activeface 50 is directed outwardly. The recess side walls 84 is provided byrespective inclined plates 118 extending longitudinally along theassembly 112 and having reflective coatings or coverings 84. Theinclined plates 118 are fast with a holder 120 that defines alongitudinally extending slot 122 in which the photovoltaic strip 30 iscomplementarily received such that the reverse face 51 of the strip 30bears against a backing plate 124 forming part of the holder 120.

The assembly 110 further includes a heat sink 116 in the form of a setof cooling fins 114 which, in operation, have an upright orientation andspace the backing plate 124 from a reflector element on which theassembly 110 is mounted, forming a convection gap 44 (see FIG. 11)between the backing plate 124 and a fin base 126 to which the fins 114are fixed cantilever-fashion. The fins 114 are connected not only to theholder 120, but also to the inclined plates 118, to form buttress-likesupports for the inclined plates 118.

Similar to the embodiment described with reference to FIGS. 1-5, holder120 may comprise sections 128 separated by thermal expansion gaps 42,the expansion gaps 42 extending through the inclined plates 118. Eachholder section 128 is fast with the cooling fins 114. Although not shownin FIGS. 10-12, the cooling fins 114 may be connected together andsupported by a stiffening plate similar to the stiffening plate 46 ofFIGS. 4 and 5.

In operation, the modular assembly 110 functions similarly to themodular assembly 20 of FIGS. 1-5, with the additional feature that themodular assembly 110 includes a secondary optic device provided by thereflective inclined plates 118. The assembly 110 is removably and/orreplaceably mountable on a reflector element comprising a plate member18 (FIGS. 1 and 2), to permit removal and replacement of the assembly110 when the lifetime of the photovoltaic strip 30 expires. The assembly110 can be reconditioned off-site by sliding removal and replacement ofthe photovoltaic strip 30 from the slot 122. As mentioned above, thephotovoltaic strip 30 may be connected to the backing plate 124 by athermally conductive adhesive. Is to be noted, however, that in otherembodiments, the heat sink may be integrally formed with a reflectorelement, so that it does not form part of any removable and replaceablecomponent.

In FIG. 12, reference numeral 130 indicates another example embodimentof a photovoltaic assembly which incorporates a heat sink 116 and asecondary optic device 112. The assembly 130 is similar in constructionand operation to the assembly 110 described with reference to FIG. 11,except that the divergent reflective side walls 84 of the secondaryoptic device 112 describe a narrower angle between them than is the casein the assembly 110 of FIG. 10.

A photovoltaic device, a mounting unit, and a method of converting solarradiation to electrical power have been described. Although theembodiments have been described with reference to specific exampleembodiments, it will be evident that various modifications and changesmay be made to these embodiments without departing from the broaderscope of the invention. Accordingly, the specification and drawings areto be regarded in an illustrative rather than a restrictive sense.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separate embodiment.

1. A photovoltaic device comprising: an array of elongate reflectorelements mounted substantially parallel to one another and transverselyspaced in series, at least one of the reflector elements having anelongate concave reflective surface disposed towards a forward adjacentreflector element in the array, the at least one reflector elementincluding: a photovoltaic receptor mounted on the reflector element by amounting arrangement, the photovoltaic receptor receiving reflectedsolar radiation from a rearward adjacent reflector element; and a heatsink in heat transfer relationship with the photovoltaic receptor,thermally isolating the photovoltaic receptor, at least partially, fromthe reflector element.
 2. The device according to claim 1, wherein themounting arrangement spaces the photovoltaic receptor from the reflectorelement, providing a convection gap between the reflector element andthe photovoltaic receptor, the heat sink forming part of the mountingarrangement and being located, at least partially, in the convectiongap.
 3. The device according to claim 2, wherein the photovoltaicreceptor is mounted on the associated reflector element adjacent anoperatively upper edge of the reflector element.
 4. The device accordingto claim 2, wherein the heat sink comprises a set of cooling fins whichare substantially parallel to one another and are transversely spaced inseries along a length of the reflector element, the cooling fins lyingin respective planes transverse to the length of the reflector element.5. The device according to claim 4, wherein the photovoltaic receptor isan elongate photovoltaic strip, the mounting arrangement including anelongate holder engaged with the photovoltaic strip, the mountingarrangement further including a thermal expansion arrangement.
 6. Thedevice according to claim 5, wherein the holder comprises a series ofholder sections longitudinally aligned and arranged end-to-end in seriesalong the length of the photovoltaic strip, adjacent ends of neighboringholder sections spaced by an expansion gap.
 7. The device according toclaim 6, wherein two or more of the holder sections are fast with aplurality of the cooling fins, the cooling fins being anchored at theirproximal ends to a base and the two or more holder sections respectivelyconnected to distal ends of the associated cooling fins.
 8. The deviceaccording to claim 1, wherein at least one of the reflector elements hasa secondary optic device directing solar radiation reflected on to it bya rearward adjacent reflector element on to the associated photovoltaicreceptor.
 9. The device according to claim 8, wherein the secondaryoptic device comprises at least one secondary reflector fast with theassociated reflector element.
 10. The device according to claim 9,wherein the photovoltaic receptor extends longitudinally along theassociated reflector element, the secondary optic device includingsecondary reflectors bordering the photovoltaic receptor and extendingalong opposite sides of the photovoltaic receptor.
 11. The deviceaccording to claim 9, wherein the secondary optic device includes anelongate recess in which the photovoltaic receptor is located, therecess having an open mouth facing toward a rearward adjacent reflectorelement, and the recess having reflective interior walls forming thesecondary reflector.
 12. A mounting unit comprising: a connectionarrangement engageable with a reflector element forming part of an arrayof elongate reflector elements mounted substantially parallel to oneanother and transversely spaced in series, at least one of the reflectorelements having an elongate concave reflective surface to reflect solarradiation on to a photovoltaic receptor mounted on an adjacent reflectorelement in the array; an elongate photovoltaic receptor holder fast withthe connection arrangement; and a heat sink operatively connected to thephotovoltaic receptor holder and in heat transfer relationship with thephotovoltaic receptor holder, thermally isolating the photovoltaicreceptor holder, at least partially, from the connection arrangement.13. The unit according to claim 12, wherein the connection arrangementincludes a snapfit formation engageable with a complementary snapfitformation on the reflector element.
 14. The unit according to claim 12,further comprising a secondary optic device directing solar radiationreflected on to it to a photovoltaic receptor held by the photovoltaicreceptor holder.
 15. A photovoltaic device comprising: an array ofelongate reflector elements mounted substantially parallel to oneanother and transversely spaced in series, at least one of the reflectorelements having an elongate concave reflective surface to reflectincident solar radiation towards a forward adjacent reflector element inthe array, the at least one reflector element including: a photovoltaicreceptor mounted on the reflector element; and a secondary optic devicedirecting solar radiation reflected on to it by a rearward adjacentreflector element on to the associated photovoltaic receptor.
 16. Thedevice according to claim 15, wherein the secondary optic devicecomprises at least one secondary reflector fast with the associatedreflector element.
 17. The device according to claim 16, wherein thephotovoltaic receptor extends longitudinally along the associatedreflector element, the secondary optic device including secondaryreflectors bordering the photovoltaic receptor and extending alongopposite sides of the photovoltaic receptor.
 18. The device according toclaim 17, wherein the secondary optic device includes an elongate recessin which the photovoltaic receptor is located, the recess having an openmouth facing toward a rearward adjacent reflector element, and therecess having reflective interior walls forming the secondary reflector.19. The device according to claim 15, further comprising a heat sink inheat transfer relationship with the photovoltaic receptor, thermallyisolating the photovoltaic receptor, at least partially, from thereflector element.
 20. The device according to claim 19, furthercomprising a convection gap between the reflector element and thephotovoltaic receptor, the heat sink being located, at least partially,in the convection gap.